(1) Field of the Invention
This invention is in the field of optical angle measuring devices, and in particular those devices which provide a high contrast direct reading of the composite angle, or its constituents, between an observer's line-of-sight and the normal to a planar surface intersected thereby.
(2) Description of the Prior Art
Conventionally, the magnitude of the composite angle, the compound angle between a line-of-sight and the normal to a planar surface, or the constituent angles, the individual angles forming the composite, are determined by a combination of mechanical distance and angle measurements. The process of making such measurements is not only tedious but fraught with opportunities to introduce errors considering the number and interrelationship of the measurements required.
The human factors engineer is often confronted with this problem, occurring with particular frequency when the line-of-sight of a pilot-observer is being analyzed during the design or verification testing of an instrument layout in an aircraft cockpit. Since there are a large number of individual instruments and panels, each of which must conform to the established standard, and the observer is defined to view from any point within an entire envelope of head positions, the evaluation of a single cockpit layout becomes a formidable task when protractors, rulers and the laws of geometry are the available tools.